Logical positivism
Logical positivism (also known as logical empiricism, scientific philosophy, and neo-positivism) is a philosophy that combines empiricism—the idea that observational evidence is indispensable for knowledge—with a version of rationalism incorporating mathematical and logico-linguistic constructs and deductions of epistemology. It may be considered as a type of analytic philosophy.See, e.g., : "Vienna Circle" in Stanford Encyclopedia of Philosophy Logical positivism, in the formal sense, began from discussions of a group known as the First Vienna Circle which gathered during the earliest years of the 20th century in Vienna at the Café Central. After World War I, Hans Hahn, a member of that early group, helped bring Moritz Schlick to Vienna. Schlick's Vienna Circle, along with Hans Reichenbach's Berlin Circle, propagated the new doctrines more widely during the 1920s and early 1930s. It was Otto Neurath's advocacy that made the movement self-conscious and more widely known. A 1929 pamphlet written by Neurath, Hahn, and Rudolf Carnap summarized the doctrines of the Vienna Circle at that time. The doctrines included the opposition to all metaphysics, especially ontology and synthetic a priori propositions; the rejection of metaphysics not as wrong but as having no meaning; a criterion of meaning based on Ludwig Wittgenstein's early work; the idea that all knowledge should be codifiable by a single standard language of science; and above all the project of rational reconstruction, in which ordinary-language concepts were gradually to be replaced by more precise equivalents in that standard language. It was an important philosophical development for psychologists as it contributed to supporting the development of behaviorism Kock, S (1`964). Psychology and emerging conceptions of knowledge as unitary. In T. Wann (ed) Behaviorism and Phenomenolgy (pp1-45) Chicago:University of Chicago Press although the strength of this relationship can be overstated. Smith, L.D. (1986). Behaviourism and logical positivism.:A reassessment of the alliance. Stanford:Stanford University Press Summary During the late 1920s, '30s, and '40s, Bertrand Russell and Ludwig Wittgenstein's formalism was developed by a group of philosophers in Vienna and Berlin, who formed the Vienna Circle and Berlin Circle into a doctrine known as logical positivism (or logical empiricism). Logical positivism used formal logic to underpin an empiricist account of our knowledge of the world. Philosophers such as Rudolf Carnap and Hans Reichenbach, along with other members of the Vienna Circle, claimed that the truths of logic and mathematics were tautologies, and those of science were verifiable empirical claims. These two constituted the entire universe of meaningful judgements; anything else was nonsense. The claims of ethics and aesthetics were subjective preferences. Theology and other metaphysics were pseudo-statements, neither true nor false, simply meaningless nonsense. Karl Popper's insistence upon the role of falsification in the philosophy of science was a reaction to the logical positivists. With the rise of Adolf Hitler and National Socialism in Germany and Austria, some members of the Vienna and Berlin Circles fled Germany, mainly to Britain and the USA, which helped to reinforce the dominance of logical positivism and analytic philosophy in the Anglophone world.Prominent amongst these were Ludwig Wittgenstein and Rudolf Carnap. Karl Popper might also be included, since despite his rejection of the term his method has much in common with the analytic tradition. Logical positivists typically considered philosophy as having a very limited function. For them, philosophy is concerned with the organization of thoughts, rather than having distinct topics of its own. The positivists adopted the principle of verificationism, according to which every meaningful statement is either analytic or is capable of being verified by experience. This caused the logical positivists to reject many traditional problems of philosophy, especially those of metaphysics or ontology, as meaningless. Origins The chief influences on the early logical positivists were Ernst Mach and Ludwig Wittgenstein. Mach's influence is most apparent in the logical positivists' persistent concern with metaphysics, the unity of science, and the interpretation of the theoretical terms of science, as well as the doctrines of reductionism and phenomenalism, later abandoned by many positivists. Wittgenstein's Tractatus was a text of great importance for the positivists. The use of the tools of modern logic for linguistic reform, the conception of philosophy as a "critique of language," and the possibility of drawing a theoretically principled distinction between intelligible and nonsensical discourse were all appealing to the logical positivists. Many positivists adopted a correspondence theory of truth similar to that of the Tractatus, although some, like Otto Neurath, preferred a form of coherentism. Wittgenstein's influence is further evident in certain formulations of the verification principle. Compare, for example, Proposition 4.024 of the Tractatus, where Wittgenstein asserts that we understand a proposition when we know what happens if it is true, with Schlick's assertion that "To state the circumstances under which a proposition is true is the same as stating its meaning"."Positivismus und Realismus", Erkenntnis 3:1-31, English trans. in Sarkar, Sahotra (ed.) Logical Empiricism at its Peak: Schlick, Carnap, and Neurath. New York: Garland Pub., 1996, p. 38 The tractarian doctrine that the truths of logic are tautologies was widely held among the logical positivists. Wittgenstein also influenced the logical positivists' interpretation of probability. It should be noted that not all logical positivists' reactions to the Tractatus were positive; according to Neurath, it was full of metaphysics.For a very informative and somewhat cute summary of the effect the Tractatus had on the leading logical positivists, see the Entwicklung der Thesen des "Wiener Kreises" Contemporary developments in logic and the foundations of mathematics, especially Russell and Whitehead's monumental Principia Mathematica, impressed the more mathematically minded logical positivists such as Hans Hahn and Rudolf Carnap. "Language-planning" and syntactical techniques derived from these developments were used to defend logicism in the philosophy of mathematics and various reductionist theses. Russell's theory of types was employed to explosive effect in Carnap's early anti-metaphysical polemics.Carnap, op. cit. Immanuel Kant was something of a punching bag in many of the logical positivists' early debates, but his influence shows through. His doctrine of synthetic a priori truths was the view to overthrow, and his notion of the thing in itself commanded its fair share of attention. More positively, Kantian views about the nature of physical objects pervade the "protocol sentence" debateSee the essays by Carnap and Neurath in Ayer's Logical Positivism., and the positivists all shared somewhat Kantian views about the relationship between philosophy and science.Friedman, Michael, Reconsidering Logical Positivism. Cambridge, UK: Cambridge University Press, 1999. Basic tenets Although the logical positivists held a wide range of beliefs on many matters, they were all interested in science and skeptical of theology and metaphysics. Early on, most logical positivists believed that all knowledge is based on logical inference from simple "protocol sentences" grounded in observable facts. Many logical positivists supported forms of materialism, philosophical naturalism, and empiricism. Perhaps the view for which the logical positivists are best known is the verifiability criterion of meaning, or verificationism. In one of its earlier and stronger formulations, this is the doctrine that a proposition is "cognitively meaningful" only if there is a finite procedure for conclusively determining whether it is true or false. For a classic survey of other versions of verificationism, see Hempel, Carl. "Problems and Changes in the Empiricist Criterion of Meaning." Revue Internationale de Philosophie 41 (1950), pp 41-63. An intended consequence of this view, for most logical positivists, is that metaphysical, theological, and ethical statements fall short of this criterion, and so are not cognitively meaningful. For the classic expression of this view, see Carnap, Rudolf. "The Elimination Of Metaphysics Through Logical Analysis of Language." Erkenntnis 2 (1932). Rpt. in Logical Positivism. Ed. Alfred Jules Ayer. New York: Free Press, 1959. 60-81. Moritz Schlick, a key figure in the logical positivist movement, did not believe ethical (or aesthetic) sentences to be cognitively meaningless. See Schlick, Moritz. "The Future Of Philosophy." The Linguistic Turn. Ed. Richard Rorty. Chicago: University of Chicago Press, 1992. 43-53. They distinguished cognitive from other varieties of meaningfulness (e.g. emotive, expressive, figurative), and most authors concede that the non-cognitive statements of the history of philosophy possess some other kind of meaningfulness. The positive characterization of cognitive meaningfulness varies from author to author. It has been described as the property of having a truth value, corresponding to a possible state of affairs, naming a proposition, or being intelligible or understandable in the sense in which scientific statements are intelligible or understandable. Examples of these different views can be found in Scheffler's Anatomy of Inquiry, Ayer's Language, Truth, and Logic, Schlick's "Positivism and Realism" (rpt. in Sarkar (1996) and Ayer (1959)), and Carnap's Philosophy and Logical Syntax. Another characteristic feature of logical positivism is the commitment to "Unified Science"; that is, the development of a common language or, in Neurath's phrase, a "universal slang" in which all scientific propositions can be expressed.For a thorough consideration of what the thesis of the unity of science amounts to, see Frost-Arnold, Gregory, "The Large-Scale Structure of Logical Empiricism: Unity of Science and the Rejection of Metaphysics" at http://philsci-archive.pitt.edu/archive/00002005/01/PSA2004Short.rtf The adequacy of proposals or fragments of proposals for such a language was often asserted on the basis of various "reductions" or "explications" of the terms of one special science to the terms of another, putatively more fundamental one. Sometimes these reductions took the form of set-theoretic manipulations of a handful of logically primitive concepts;As in Carnap's (1928) Logical Structure of the World. sometimes these reductions took the form of allegedly analytic or a priori deductive relationships.As in Carnap's Testability and Meaning. A number of publications over a period of thirty years would attempt to elucidate this concept. ''Einheitswissenschaft'' The Vienna Circle published a collection called Einheitswissenschaft (Unified Science)—edited by Rudolf Carnap, Philipp Frank, Hans Hahn, Otto Neurath, Jorgen Jorgensen (after Hahn's death) and Charles Morris—the aim of which was to present a unified vision of science. The collection was dismissed, after the publication of several monographies, because of the problems arising from World War II. The list of philosophers and scientists who contributed to these works is impressive. The complete list of contributors is given here for the historical record. Einheitswissenschaft (Unified Science), edited by Carnap, Frank, Hahn, Neurath, Jorgensen (after Hahn's death), and Morris (from 1938): *Hans Hahn, Logik, Mathematik und Naturerkennen, 1933 *Otto Neurath, Einheitswissenschaft und Psychologie, 1933 *Rudolf Carnap, Die Aufgabe der Wissenschaftlogik, 1934 *Philipp Frank, Das Ende der mechanistischen Physik, 1935 *Otto Neurath, Was bedeutet rationale Wirtschaftsbetrachtung, 1935 *Otto Neurath, E. Brunswik, C. Hull, G. Mannoury, J. Woodger, Zur Enzyklopädie der Einheitswissenschaft. Vorträge, 1938 *Richard von Mises, Ernst Mach und die empiristische Wissenschaftauffassung, 1939 These works are translated in Unified Science: The Vienna Circle Monograph Series, originally edited by Otto Neurath:, Kluwer, 1987. ''International Encyclopedia of Unified Science'' In 1938 the publication of the International Encyclopedia of Unified Science started under the auspice of logical positivists. It was an ambitious project, and never completed. Only the first section, Foundations of the Unity of Sciences, was published; it contained two volumes, for a total of twenty monographs published from 1938 to 1969: *Otto Neurath, Niels Bohr, John Dewey, Bertrand Russell, Rudolf Carnap, Charles Morris, Encyclopedia and unified science, 1938, vol.1 n.1 *Charles Morris, Foundations of the theory of signs, 1938, vol.1 n.2 *Victor Lenzen, Procedures of empirical sciences, 1938, vol.1 n.5 *Rudolf Carnap, Foundations of logic and mathematics, 1939, vol.1 n.3 *Leonard Bloomfield, Linguistic aspects of science, 1939, vol.1 n.4 *Ernest Nagel, Principles of the theory of probability, 1939, vol.1 n.6 *John Dewey, Theory of valuation, 1939, vol.2 n.4 *Giorgio De Santillana and Egdard Zilsel, The development of rationalism and empiricism, 1941, vol.2 n.8 *Otto Neurath, Foundations of social sciences, 1944, vol.2 n.1 *Joseph Henri Woodger, The technique of theory construction, 1949, vol.2 n.5 *Philipp Frank, Foundations of physics, 1946, vol.1 n.7 *Erwin Frinlay-Freundlich, Cosmology, 1951, vol.1 n.8 *Jorgen Jorgensen, The development of logical empiricism, 1951, vol.2 n.9 *Egon Brunswik, The conceptual framework of psychology, 1952, vol.1 n.10 *Carl Hempel, Fundamentals of concept formation in empirical science, 1952, vol.2 n.7 *Felix Mainx, Foundations of biology, 1955, vol.1 n.9 *Abraham Edel, Science and the structure of ethics, 1961, vol.2 n.3 *Thomas Kuhn, The structure of scientific revolutions, 1962, vol.2 n.2 *Gherard Tintner, Methodology of mathematical economics and econometrics, 1968, vol.2 n.6 *Herbert Feigl and Charles Morris, Bibliography and index, 1969, vol.2 n.10 Perhaps the most famous work published in the International Encyclopedia of Unified Science is Thomas Kuhn's The Structure of Scientific Revolutions. However, every entry in the encyclopedia is of substantial scientific and philosophical value. ''Monographs on the Scientific World-Conception'' A third collection was published by the Vienna Circle from 1928 to 1937. This collection was entitled Schriften zur wissenschaftlichen Weltauffassung (Monographs on the Scientific World-Conception), and was edited by Schlick and Frank. Scientists and philosophers such as Karl Popper contributed. The contributors and monographs were: *Richard von Mises, Wahrscheinlichkeit, Statistik und Wahrheit, 1928 (Probability, Statistics, and Truth, New York: MacMillan Company, 1939) *Rudolf Carnap, Abriss der Logistik, 1929 *Moritz Schlick, Fragen der Ethik, 1930 (Problems of Ethics, New York: Prentice-Hall, 1939) *Otto Neurath, Empirische Soziologie, 1931 *Philipp Frank, Das Kausalgesetz und seine Grenzen, 1932 (The Law of Causality and its Limits, Dordrecht; Boston: Kluwer, 1997) *Otto Kant, Zur Biologie der Ethik, 1932 *Rudolf Carnap, Logische Syntax der Sprache, 1934 (The Logical Syntax of Language, New York: Humanities, 1937) *Karl Popper, Logik der Forschung, 1934 (The Logic of Scientific Discovery, New York: Basic Books, 1959) *Josef Schächeter, Prolegomena zu einer kritischen Grammatik, 1935 (Prolegomena to a Critical Grammar, Dordrecht; Boston: D. Reidel Pub. Co., 1973) *Victor Kraft, Die Grundlagen einer wissenschaftliche Wertlehre, 1937 (Foundations for a Scientific Analysis of Value, Dordrecht; Boston: D. Reidel Pub. Co., 1981) Philosophers associated with logical positivism There is an extensive list of philosophers who are associated to some degree with logical positivism. The Vienna Circle *The physicist and philosopher Moritz Schlick, one of the first philosophers interested in the theory of relativity. He taught at the University of Vienna, where he held the chair of theory of inductive science. In Vienna, he organized the discussion group known as the Vienna Circle. Schlick can be regarded as the father of logical positivism, both for his organizational skills and for his philosophical ideas. He formulated the verifiability principle. *'Rudolf Carnap', one of the major philosophers of the twentieth century, a leading exponent of logical positivism, and co-author of the Vienna Circle manifesto. He made contributions to the philosophy of science, the philosophy of language, the theory of probability, and classical, inductive and modal logic. Since ordinary language is ambiguous, Carnap asserted the necessity to study philosophical issues in artificial languages, governed by the rules of logic and mathematics. In such languages he dealt with problems like the meaning of a statement, the distinction between analytic and synthetic, a priori and a posteriori, necessity and contingency, the different interpretations of probability, and the nature of explanation. Carnap taught at the University of Prague, the University of Vienna, the University of Chicago, Harvard University, and the University of California at Los Angeles. *The philosopher of science Herbert Feigl, who encouraged Karl Popper to write the book Logik der Forschung. His 1931 article with A. E. Blumberg, "Logical Positivism: A New Movement in European Philosophy" in The Journal of Philosophy, was one of the first reports on logical positivism published in the United States, and promoted the spread of logical positivism. He taught at the University of Iowa and at the University of Minnesota, where in 1953 he founded the Minnesota Center for the Philosophy of Science, the oldest center for the philosophy of science in the world. *The physicist Philipp Frank, a student of David Hilbert and Ludwig Boltzmann, who was an editor of the series Monographs on the Scientific World-Conception and Unified Science; he contributed to the International Encyclopedia of Unified Science with the 1946 work "Foundations of physics".. He taught at Harvard University and wrote about the theory of relativity. *The logician and mathematician Kurt Gödel attended meetings of the Vienna Circle weekly between 1926 and 1928, but, although he is sometimes mistaken for a positivist, and his greatest achievements "are still often tallied among positivism's greatest success stories" , he was actually committed to Platonism and many of his core ideas were diametrically opposed to those of the rest of the Circle. Gödel proved the completeness of first-order logic and the incompleteness of formal arithmetic. Gödel also worked on set theory and non-classical logics, such as intuitionistic logic and modal logic. He proved that the continuum hypothesis is consistent with the axioms of classical set theory. He was interested in the mathematical aspects of the theory of relativity, and proved the existence of solutions of Einstein’s relativistic equations in which time travel to the past is possible. *The mathematician Hans Hahn, co-author of the Vienna Circle manifesto, who taught at Innsbruck, Bonn and Vienna; among his students there were Karl Popper and Kurt Gödel. *The philosopher and sociologist Otto Neurath, who played an important role in the development of logical positivism. He was co-author of the manifesto of the Vienna Circle (it is supposed that he was indeed the principal author), planned and directed the International Encyclopedia of Unified Science, was an editor of the journal Erkentnnis and of the series Unified Science, and founded and directed the International Foundation for Visual Education. *The philosopher Friedrich Waismann, who was one of the few members of the Vienna Circle admitted to the meetings with Wittgenstein. He taught philosophy of mathematics and philosophy of science at the University of Cambridge and at the University of Oxford. Germany and the Berlin Circle In Germany, members of the Berlin Circle contributed in an essential way to the development of logical empiricism: *The physicist and philosopher Hans Reichenbach, the founder of the Berlin Circle. He studied with Albert Einstein, Arnold Sommerfeld, Ernst Cassirer, David Hilbert, Max Planck, and Max Born. He is one of the fathers of the frequency interpretation of probability. He taught physics at Technische Hochschule in Stuttgart, philosophy of physics at the University of Berlin; he was chief of the department of philosophy at the University of Istanbul; he taught philosophy at the University of California at Los Angeles. He wrote about the philosophical meaning of the theory of relativity, which he studied under the teaching of Albert Einstein, and quantum mechanics. *The logician and philosopher Kurt Grelling, a victim of Nazism; it is supposed that he died with his wife in the Auschwitz concentration camp in 1942, although it also has been reported that Grelling was killed in 1941 at the border between France and Spain while he was trying to escape in Spain. Grelling was a teacher in secondary school and was interested in logical problems. A semantic paradox is named after him, the Grelling paradox, formulated in 1908] by Grelling and Leonard Nelson. Grelling collaborated with Kurt Gödel and in 1936 he published an article in which he defended Gödel's theorem of incompleteness against an erroneous interpretation, according to which Gödel's theorem is indeed a paradox like Russell's paradox. *The philosopher Carl Gustav Hempel, a leading member of logical positivism. He studied philosophy with Hans Reichenbach, physics with Max Planck, logic with von Neumann and mathematics with David Hilbert. He taught in New York, at the City College and at Queens College. Later, Hempel taught at Yale University, at Princeton University and, well on in years, he continued in teaching at the University of California, Berkeley and Irvine, the Hebrew University of Jerusalem, and the University of Pittsburgh. He contributed to the International Encyclopedia of Unified Science. He is well-known for his studies on the logic of confirmation and explanation. Scandinavia *As early as 1930 Scandinavian philosophers were interested in logical positivism. Finnish Eino Kaila employed for the first time the expression "logical neopositivism" for denoting the new philosophical movements (E. Kaila, "Der logistische Neupositivismus" in Annales Universitatis Aboensis, 1930). Eino Kaila published in 1939 a work pervaded by the principles of logical positivism (The human knowledge, in Finnish). He taught philosophy at the University of Helsinki. Among his students was Georg Henrik von Wright, who published a study about logical positivism (The Logical Empiricism, 1943, in Finnish). Wright contributed to the development of modal logic and deontic logic. Finn Jaakko Hintikka, who had Wright as a teacher, pursued Carnap's studies on inductive logic. Hintikka's article "A two-dimensional continuum of inductive methods" in Aspects of inductive logic (eds. J. Hintikka and P. Suppes, 1966), extended the methods Carnap used in The Continuum of Inductive Methods, 1952. Swedish philosopher Åke Petzäll (author of Der logistische Neupositivismus, 1931) was mainly influenced by the Vienna Circle and in 1930 or 1931 he went to Vienna, where he took part in theVienna Circle's meetings. Later he founded a new journal, Theoria, published in Göteborg; in that journal Hempel published his very first description of the paradoxes of confirmation (Le problème de la vérité, 1937). *Danish philosopher Jørgen Jørgensen very actively collaborated with neopositivists. After Hans Hahn's death in 1934, Jørgensen became an editor of the Vienna Circle's series Unified Science; later he collaborated on the International Encyclopedia of Unified Science, to which he contributed the 1951 essay The Development of Logical Empiricism. *In Norway, the young Arne Naess was strongly influenced by logical positivism, especially so in his doctorate Erkenntnis und wissenschaftliches Verhalten (1936). This lead to a forceful postivist bent for parts of Norwegian philosophy. United Kingdom *English philosopher Alfred Jules Ayer played an important role in the spread of logical positivism. His 1936 work Language, Truth and Logic gained immediate success. In that book, he completely accepted both the verifiability principle and the distinction between analytic and synthetic statements; hence he asserted that metaphysical sentences are meaningless. Poland *Logical positivism had extensive contacts with the group of Polish logicians who developed several branches of contemporary logic. Polish philosophy was greatly influenced by Kazimierz Twardowski, who studied at the University of Vienna and taught at Lwow; he is the founder of Polish analytic philosophy. He taught several Polish philosophers and logicians. Among them were: **'Jan Łukasiewicz', who developed both the algebra of logic and many-valued propositional calculus, which influenced Carnap's inductive logic and Reichenbach's interpretation of quantum mechanics, in which Reichenbach employed a three-valued propositional calculus. He contributed to Erkenntnis, the journal of logical positivism, edited by Carnap and Reichenbach. **'Stanisław Leśniewski', who was interested in the logical antinomies. **'Kazimierz Ajdukiewicz', who taught philosophy of language, epistemology and logic, and contributed to Erkenntnis. **'Tadeusz Kotarbiński', who asserted that many alleged philosophical problems in fact are scientific problems, i.e. they are the object of empirical science and not of philosophy, which deals with logical and ethical problems only. *The Polish logician Alfred Tarski, who developed the theory of semantics in formal language, took part in the congresses on scientific philosophy organized by the Vienna and Berlin Circles; he greatly influenced Carnap's philosophy of language. Carnap was interested in logical syntax but, after the publication of Tarski's works, he turned to semantics. Italy Relations between Italian philosophy and logical positivism developed in the early stages of logical positivism. *The Italian mathematician and philosopher of science Federigo Enriques took part in the congresses on scientific philosophy and collaborated on the International Encyclopedia, and Neurath and Carnap contributed articles to the journal Scientia edited by Enriques. *In 1934, Ludovico Geymonat published a work on logical positivism: La Nuova Filosofia della Natura in Germania. Geymonat had the opportunity to study with Schlick, Reichenbach, Carnap, and Waismann. He later held the first chair in Italy of philosophy of science. *The interest of Italian philosophy in logical positivism was primarily directed towards historical research. Francesco Barone distinguished himself with his work Il Neopositivismo Logico, 1953, a detailed and up-to-date historical and philosophical analysis of logical positivism. Criticism and influences Early critics of logical positivism said that its fundamental tenets could not themselves be formulated in a way that was clearly consistent. The verifiability criterion of meaning did not seem verifiable; but neither was it simply a logical tautology, since it had implications for the practice of science and the empirical truth of other statements. This presented severe problems for the logical consistency of the theory. Another problem was that, while positive existential claims ("there is at least one human being") and negative universals ("not all ravens are black") allow for clear methods of verification (find a human or a non-black raven), negative existential claims and positive universal claims do not allow for verification. Universal claims could apparently never be verified: How can you tell that all ravens are black, unless you've hunted down every raven ever, including those in the past and future? This led to a great deal of work on induction, probability, and "confirmation", which combined verification and falsification. Karl Popper, a well-known critic of logical positivism, published the book Logik der Forschung in 1934 (translated by himself as The Logic of Scientific Discovery published 1959). In it he presented an influential alternative to the verifiability criterion of meaning, defining scientific statements in terms of falsifiability. First, though, Popper's concern was not with distinguishing meaningful from meaningless statements, but distinguishing "scientific" from "metaphysical" statements. He did not hold that metaphysical statements must be meaningless; neither did he hold that a statement that in one century was "metaphysical" while unfalsifiable (like the ancient Greek philosophy about atoms), could not in another century become "falsifiable" and thus "scientific". About psychoanalysis he thought something similar: in his day it offered no method for falsification, and thus was not falsifiable and not scientific. However, he did not exclude it being meaningful, nor did he say psychoanalysts were necessarily "wrong" (it only couldn't be proven either way: that would have meant it was falsifiable), nor did he exclude that one day psychoanalysis could evolve into something falsifiable, and thus "scientific". He was, in general, more concerned with scientific practice than with the logical issues that troubled the positivists. Second, although Popper's philosophy of science enjoyed great popularity for some years, if his criterion is construed as an answer to the question the positivists were asking, it turns out to fail in exactly parallel ways. Negative existential claims ("there are no unicorns") and positive universals ("all ravens are black") can be falsified, but positive existential and negative universal claims cannot, although Popper thought himself these could be deemed as verifiablePopper, K., The Logic of Scientific Discovery, chapter 13. Logical positivists' response to the first criticism is that logical positivism is a philosophy of science, not an axiomatic system that can prove its own consistency (see Gödel's incompleteness theorem). Secondly, a theory of language and mathematical logic were created to answer what it really means to make statements like "all ravens are black". A response to the second criticism was provided by A. J. Ayer in Language, Truth and Logic, in which he sets out the distinction between "strong" and "weak" verification. "A proposition is said to be verifiable, in the strong sense of the term, if, and only if, its truth could be conclusively established by experience." (Ayer 1946:50) It is this sense of verifiable that causes the problem of verification with negative existential claims and positive universal claims. However, the weak sense of verification states that a proposition is "verifiable... if it is possible for experience to render it probable" (ibid.). After establishing this distinction, Ayer goes on to claim that "no proposition, other than a tautology, can possibly be anything more than a probable hypothesis" (Ayer 1946:51), and therefore can only be subject to weak verification. This defense was controversial among logical positivists, some of whom stuck to strong verification, and claimed that general propositions were indeed nonsense. Subsequent philosophy of science tends to make use of certain aspects of both of these approaches. W. V. O. Quine criticized the distinction between analytic and synthetic statements and the reduction of meaningful statements to immediate experience. Work by Thomas Kuhn has convinced many that it is not possible to provide truth conditions for science independent of its historical paradigm. But even this criticism was not unknown to the logical positivists: Otto Neurath compared science to a boat which we must rebuild on the open sea. Logical positivism was essential to the development of early analytic philosophy. It was disseminated throughout the European continent and, later, in American universities by the members of the Vienna Circle. A.J. Ayer is considered responsible for the spread of logical positivism to Britain. The term subsequently came to be almost interchangeable with "analytic philosophy" in the first half of the twentieth century. Logical positivism was immensely influential in the philosophy of language and represented the dominant philosophy of science between World War I and the Cold War. Many subsequent commentators on "logical positivism" have attributed to its proponents a greater unity of purpose and creed than they actually shared, overlooking the complex disagreements among the logical positivists themselves. Footnotes Further reading *Achinstein, Peter and Barker, Stephen F. The Legacy of Logical Positivism: Studies in the Philosophy of Science. Baltimore: Johns Hopkins Press, 1969. *Ayer, Alfred Jules. Logical Positivism. Glencoe, Ill: Free Press, 1959. *Barone, Francesco. Il neopositivismo logico. Roma Bari: Laterza, 1986. *Bergmann, Gustav. The Metaphysics of Logical Positivism. New York: Longmans Green, 1954. *Cirera, Ramon. Carnap and the Vienna Circle: Empiricism and Logical Syntax. Atlanta, GA: Rodopi, 1994. *Edmonds, David & Eidinow, John; Wittgenstein's Poker, ISBN 0-06-621244-8 *Friedman, Michael. Reconsidering Logical Positivism. Cambridge, UK: Cambridge University Press, 1999 *Gadol, Eugene T. Rationality and Science: A Memorial Volume for Moritz Schlick in Celebration of the Centennial of his Birth. Wien: Springer, 1982. *Geymonat, Ludovico. La nuova filosofia della natura in Germania. Torino, 1934. *Giere, Ronald N. and Richardson, Alan W. Origins of Logical Empiricism. Minneapolis: University of Minnesota Press, 1997. *Hanfling, Oswald. Logical Positivism. Oxford: B. Blackwell, 1981. *Jangam, R. T. Logical Positivism and Politics. Delhi: Sterling Publishers, 1970. *Janik, Allan and Toulmin, Stephen. Wittgenstein's Vienna. London: Weidenfeld and Nicolson, 1973. *Kraft, Victor. The Vienna Circle: The Origin of Neo-positivism, a Chapter in the History of Recent Philosophy. New York: Greenwood Press, 1953. *McGuinness, Brian. Wittgenstein and the Vienna Circle: Conversations Recorded by Friedrich Waismann. Trans. by Joachim Schulte and Brian McGuinness. New York: Barnes & Noble Books, 1979. *Mises von, Richard. Positivism: A Study in Human Understanding. Cambridge: Harvard University Press, 1951. *Parrini, Paolo. Empirismo logico e convenzionalismo: saggio di storia della filosofia della scienza. Milano: F. Angeli, 1983. *Parrini, Paolo; Salmon, Wesley C.; Salmon, Merrilee H. (ed.) Logical Empiricism - Historical and Contemporary Perspectives, Pittsburgh: University of Pittsburgh Press, 2003. *Reisch, George. How the Cold War Transformed Philosophy of Science : To the Icy Slopes of Logic. New York: Cambridge University Press, 2005. *Rescher, Nicholas. The Heritage of Logical Positivism. Lanham, MD: University Press of America, 1985. *Salmon, Wesley and Wolters, Gereon (ed.), Logic, Language, and the Structure of Scientific Theories: Proceedings of the Carnap-Reichenbach Centennial, University of Konstanz, 21-24 May 1991, Pittsburgh: University of Pittsburgh Press, 1994. *Sarkar, Sahotra. The Emergence of Logical Empiricism: From 1900 to the Vienna Circle. New York: Garland Publishing, 1996. *Sarkar, Sahotra. Logical Empiricism at its Peak: Schlick, Carnap, and Neurath. New York: Garland Pub., 1996. *Sarkar, Sahotra. Logical Empiricism and the Special Sciences: Reichenbach, Feigl, and Nagel. New York: Garland Pub., 1996. *Sarkar, Sahotra. Decline and Obsolescence of Logical Empiricism: Carnap vs. Quine and the Critics. New York: Garland Pub., 1996. *Sarkar, Sahotra. The Legacy of the Vienna Circle: Modern Reappraisals. New York: Garland Pub., 1996. *Spohn, Wolfgang (ed.), Erkenntnis Orientated: A Centennial Volume for Rudolf Carnap and Hans Reichenbach, Boston: Kluwer Academic Publishers, 1991. See also People *Kazimierz Ajdukiewicz *Alfred Jules Ayer *Richard Bevan Braithwaite *Rudolf Carnap *Herbert Feigl *Philipp Frank *Kurt Grelling *Hans Hahn *Carl Gustav Hempel *Tadeusz Kotarbinski *Thomas Kuhn *Stanislaw Lesniewski *Jan Lukasiewicz *Ernest Nagel *Otto Neurath *Karl Raimund Popper *Hans Reichenbach *Moritz Schlick *Alfred Tarski *Kazimierz Twardowski *Friedrich Waismann *Ludwig Wittgenstein *David Rynin Institutions *Berlin Circle *Vienna Circle Other philosophical movements *Positivism *Sociological positivism *Verificationist External links About logical positivism * [http://etext.lib.virginia.edu/cgi-local/DHI/dhicontrib2.cgi?id=dv3-69 Feigl, Herbert. 'Positivism in the Twentieth Century (Logical Empiricism)', Dictionary of the History of Ideas, 1974, Gale Group (Electronic Edition)] * [http://www.philosophypages.com/hy/6q.htm Kemerling, Garth. 'Logical Positivism', Philosophy Pages] * [http://www.murzim.net/Articles/Positivism.pdf Murzi, Mauro. 'Logical Positivism', The New Encyclopedia of Unbelief, Tom Flynn (ed.). Prometheus Books, forthcoming (PDF version)] * Murzi, Mauro. 'The Philosophy of Logical Positivism' * [http://www.comnet.ca/~pballan/logicalpos(Passmore).htm Passmore, John. 'Logical Positivism', The Encyclopedia of Philosophy, Paul Edwards (ed.). New York: Macmillan, 1967, first edition] * Shalizi, Cosma Rohilla. 'Logical Positivism' * Logical positivism About philosophical subjects pertinent to logical positivism * [http://plato.stanford.edu/archives/sum2003/entries/probability-interpret/ Hájek, Alan. 'Interpretations of Probability', The Stanford Encyclopedia of Philosophy (Summer 2003 Edition), Edward N. Zalta (ed.)] * [http://plato.stanford.edu/archives/fall2003/entries/analytic-synthetic/ Rey, Georges. 'The Analytic/Synthetic Distinction', The Stanford Encyclopedia of Philosophy (Fall 2003 Edition), Edward N. Zalta (ed.)] * [http://plato.stanford.edu/archives/win2001/entries/genrel-early/ Ryckman, Thomas A., 'Early Philosophical Interpretations of General Relativity', The Stanford Encyclopedia of Philosophy (Winter 2001 Edition), Edward N. Zalta (ed.)] * [http://plato.stanford.edu/archives/sum2003/entries/lvov-warsaw/ Woleński, Jan. 'Lvov-Warsaw School', The Stanford Encyclopedia of Philosophy (Summer 2003 Edition), Edward N. Zalta (ed.)] * [http://plato.stanford.edu/archives/sum2003/entries/scientific-explanation/ Woodward, James. 'Scientific Explanation', The Stanford Encyclopedia of Philosophy (Summer 2003 Edition), Edward N. Zalta (ed.)] Category:Philosophical schools and traditions Category:Philosophical movements Category:Philosophy of language Category:Epistemology Category:Philosophy of science